Heat-receiving member and exhaust pipe heat-releasing system

ABSTRACT

A heat-receiving member includes a base and a surface layer. The base has a surface and includes at least one of aluminum and an aluminum alloy. The surface layer is provided at the surface of the base. The surface layer is anodized.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2008-179380, filed Jul. 9, 2008, the contents of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat-receiving member and an exhaust pipe heat-releasing system.

2. Discussion of the Background

An exhaust pipe connected to a vehicle engine becomes significantly hot in driving operation because combustion gases (exhaust gases) flow therethrough. In a high-load and high-revolution area of the engine, fuel is increased so as to avoid a rise in temperature of exhaust gases. In such a case, however, a problem arises that the fuel efficiency is lowered and the concentration of exhaust gases is raised, so that the discharge amount of contaminants is increased.

Further, when the temperature of the exhaust pipe is raised by a flow of exhaust gases, it causes heat degradation of the exhaust pipe.

Inside an exhaust pipe, a catalyst is provided for converting exhaust gases discharged from a vehicle engine. For example, a three-way catalyst can convert contaminants such as hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) which are contained in exhaust gases.

In order to convert these contaminants by a three-way catalyst more efficiently, it is necessary to maintain the three-way catalyst at a predetermined activation temperature.

It is desirable that, in the high-speed operation of the vehicle engine, the temperature of the exhaust pipe connected to a vehicle engine not rise too high and the exhaust pipe be appropriately cooled.

JP-A 6-336923 discloses a heat insulator that can appropriately cool an exhaust pipe connected to a vehicle engine.

The contents of JP-A 6-336923 are incorporated herein by reference in their entirety.

FIG. 1 is an exploded perspective view which illustrates a vehicle engine and a vicinity of an exhaust pipe connected to the vehicle engine.

In FIG. 1, “110” indicates an engine and a cylinder head 117 is mounted on a top of a cylinder block 116 of the vehicle engine 110. Further, an exhaust manifold 111, which contains cast iron with high heat resistance, is attached on one side face of the cylinder head 117.

The exhaust manifold 111 has a function of gathering exhaust gases from respective cylinders and transferring the exhaust gases to a not-shown catalyst converter and the like. That is, the exhaust manifold 111 functions as an exhaust pipe through which exhaust gases from the engine flow.

Part of the outer peripheral face of the exhaust manifold 111 is covered with a heat insulator 118. The heat insulator 118 is arranged over the outer peripheral face of the exhaust manifold 111 with a predetermined space therebetween.

JP-A 6-336923 sets the emissivity of the heat insulator to be more than the emissivity of the exhaust manifold. JP-A 6-336923 describes that setting the relationships of the emissivities as such increases the amount of radiation heat transferred between the exhaust manifold and the heat insulator, and thus improves the cooling ability of the exhaust manifold.

JP-A 6-336923 also describes that a black, heat-resistant coating is applied to the heat insulator that is made of cast iron so as to improve the emissivity of the heat insulator.

Recently, aluminum or an aluminum alloy (hereinafter referred also to simply as aluminum) has often been used as a material for a heat insulator in order to reduce the vehicle body weight, and the like.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a heat-receiving member includes a base and a surface layer. The base has a surface and includes at least one of aluminum and an aluminum alloy. The surface layer is provided at the surface of the base. The surface layer is anodized.

According to another aspect of the present invention, an exhaust pipe heat-releasing system includes an exhaust pipe and a heat-receiving member. The exhaust pipe includes a metal. The heat-receiving member is arranged to face a periphery of the exhaust pipe to receive heat energy released from the exhaust pipe. The heat-receiving member includes a base and a surface layer. The base has a surface and includes at least one of aluminum and an aluminum alloy. The surface layer is provided at the surface of the base. The surface layer is anodized.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

FIG. 1 is an exploded perspective view which illustrates a vehicle engine and a vicinity of an exhaust pipe connected to the vehicle engine.

FIG. 2 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 5 is a cross-sectional view schematically illustrating an exemplary exhaust pipe heat-releasing system according to an embodiment of the present invention.

FIG. 6 is a cross-sectional view schematically illustrating a method of measuring heat receiving performance of a heat-receiving member.

FIG. 7 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 8 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 9 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 10 is a view showing the relationships between the locations of temperature measurement and the temperatures of the respective heat-receiving members which were measured in Example 2 and Examples 6 to 9.

FIG. 11 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 12 is a scanning electron microscope photograph that shows a surface of a surface layer of an exemplary heat-receiving member according to an embodiment of the present invention which has cracks in the surface layer.

FIG. 13 is a scanning electron microscope photograph that shows a surface of a surface layer of an exemplary heat-receiving member according to an embodiment of the present invention which has cracks in the surface layer.

FIG. 14 is a scanning electron microscope photograph that shows a surface of a surface layer of an exemplary heat-receiving member according to an embodiment of the present invention which has cracks in the surface layer.

FIG. 15 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to an embodiment of the present invention.

FIG. 16 is a cross-sectional view schematically illustrating an exemplary exhaust pipe heat-releasing system according to an embodiment of the present invention.

FIG. 17 is an exploded perspective view schematically illustrating exemplary arrangement of a heat-receiving member according to an embodiment of the present invention as a different member from a heat insulator.

DESCRIPTION OF THE EMBODIMENTS

Embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.

A heat-receiving member according to an embodiment of the present invention receives heat energy released from a heat source, and includes: a base that contains aluminum or an aluminum alloy; and a surface layer that is formed by anodizing a surface of the base.

The heat-receiving member according to the embodiment of the present invention has the surface layer formed by anodizing the surface of the base that contains aluminum or an aluminum alloy.

The emissivity of the surface layer formed by anodizing the surface of aluminum tends to be higher than the emissivity of aluminum. High emissivity of the surface of the surface layer makes it easier for the surface layer to receive by radiation heat transfer a large amount of heat released from the heat source, when the heat-receiving member according to the embodiment of the present invention is arranged with the surface layer thereof facing the heat source such as an exhaust pipe. That is, the heat-receiving member according to the embodiment of the present invention is excellent at receiving, by radiation heat transfer, heat released from a heat source. Further, use of such a heat-receiving member makes it easier to promote heat release from the heat source.

The interface between aluminum and a surface layer formed by anodization is chemically stable and the adhesion between aluminum and the surface layer is strong. Therefore, the surface layer becomes less likely to peel off from aluminum.

In the heat-receiving member according to an embodiment of the present invention, the heat-receiving member desirably has a first region and a second region, the first region is desirably located farther from a high-temperature part of the heat source than the second region, and the first region desirably has emissivity higher than emissivity of the second region.

The first region herein also means a region far from the high-temperature part of the heat source. The second region herein means another region or a region close to the high-temperature part of the heat source.

Now, the variation of temperature distribution inside the heat-receiving member adjacent to the heat source is considered. With regard to the temperatures of respective regions in the heat-receiving member, much heat is transferred to the region close to the high-temperature part of the heat source, and thus the temperature of the region tends to rise. On the other hand, not much heat is transferred to the region far from the high-temperature part of the heat source, and thus the temperature of the region tends not to rise. As a result, a high-temperature region and a low-temperature region tend to generate inside the heat-receiving member. This temperature difference inside the heat-receiving member easily leads to generation of thermal stress in the heat-receiving member, which might distort the heat-receiving member.

The amount of heat per unit area that the region having higher emissivity than the another region in the heat-receiving member according to the embodiment of the present invention receives tends to be large because the region easily receives heat by radiation heat transfer. The region having higher emissivity than the another region is thus more likely to be a region in which the temperature tends to rise due to heat reception. Accordingly, placing the region having higher emissivity than the another region at a location far from the high-temperature part of the adjacent heat source makes it more likely for the temperature of the heat-receiving member to rise even if the region is located far from the high-temperature part of the heat source; hence, generation of a low-temperature region inside the heat-receiving member is more easily prevented.

That is, generation of a temperature difference inside the heat-receiving member is more easily prevented. Further, generation of thermal stress and distortion in the heat-receiving member is more easily prevented.

In the heat-receiving member according to an embodiment of the present invention, a micropore is desirably formed in the surface layer in the first region, and a metal is desirably deposited in the micropore.

Deposition of a metal in the micropore in the surface layer makes it easier to increase the emissivity of the region. That is, placing the region with a metal deposited in the micropore formed in the surface layer thereof at a location far from the high-temperature part of the heat source makes it easier to more effectively prevent generation of a low-temperature region inside the heat-receiving member.

In the heat-receiving member according to an embodiment of the present invention, the second region desirably includes a region in which the surface of the base is unanodized and exposed.

In this case, the emissivity of the region with the surface of the base exposed thereon tends to be low. Placing the region with the surface of the base exposed thereon at a location close to the high-temperature part of the heat source makes it easier to prevent the temperature of the heat-receiving member from rising too high even if the region is located close to the high-temperature part of the heat source; hence, generation of a high-temperature region inside the heat-receiving member is more easily prevented. That is, generation of a temperature difference inside the heat-receiving member is more easily prevented.

In the heat-receiving member according to an embodiment of the present invention, a plurality of cracks are desirably formed in the surface layer.

Here, a coefficient of thermal expansion of the surface layer formed by anodization is different from a coefficient of thermal expansion of aluminum or an aluminum alloy used as the base. Thus, a rise in the temperature of the heat-receiving member easily leads to application of thermal stress between the base and the surface layer. When the thermal stress applied between the base and the surface layer is large or the thickness of the base is small, a fissure might be generated in the base (the base might split).

Since the plurality of cracks are formed in the surface layer of the heat-receiving member according to the embodiment of the present invention, part of the thermal stress applied between the base and the surface layer is more easily absorbed at the cracked parts, whereby an increase in the thermal stress applied between the base and the surface layer is more easily prevented. As a result, generation of a fissure in the base due to the thermal stress is more easily prevented.

In the heat-receiving member according to an embodiment of the present invention, the cracks are desirably separated from each other.

The cracks separated from each other tend to absorb the thermal stress and to grow upon application of the thermal stress to the surface layer. As a result, generation of a fissure in the base is more likely to be effectively prevented. Further, the continuous surface layer is more likely to increase the rigidity and thus makes it easier for the heat-receiving member to maintain the shape.

In the heat-receiving member according to an embodiment of the present invention, at least one of the cracks desirably has a zigzag shape.

When the cracks each have a zigzag shape, resistance to the force applied in a direction parallel to the cracks is more likely to be generated. Hence, it becomes easier to prevent generation of a fissure in the base more effectively.

In the heat-receiving member according to an embodiment of the present invention, it is desirable that a surface layer be also formed on a surface on the reverse side of the surface of the base.

In this case, surface layers are formed by anodizing both respective surfaces of the heat-receiving member, and therefore the emissivity of the both surfaces of the heat-receiving member tends to be high. Then, it becomes easier for the heat-receiving member to receive much heat on one surface and release much heat from the other surface. Accordingly, the temperature of the heat-receiving member tends not to rise, whereby the thermal stress to be generated in the heat-receiving member is more easily reduced.

The lower the temperature of the heat-receiving member, the larger the amount of heat that the heat-receiving member can receive tends to be. For this reason, the temperature of the heat-receiving member is prevented from easily rising even when the heat-receiving member has received heat, and thus the heat-receiving member according to the embodiment of the present invention tends to demonstrate better performance in receiving heat by radiation heat transfer.

An exhaust pipe heat-releasing system according to an embodiment of the present invention includes: an exhaust pipe including a cylindrical base that contains a metal; and a heat-receiving member arranged over the exhaust pipe, wherein the heat-receiving member receives heat energy released from the exhaust pipe, and includes a base that contains aluminum or an aluminum alloy; and a surface layer that is formed by anodizing a surface of the base of the heat-receiving member.

The heat-receiving member according to the embodiment of the present invention demonstrates excellent performance in receiving heat by radiation heat transfer. Hence, such a heat-receiving member arranged over the exhaust pipe is more likely to receive much radiation heat from the outer peripheral face of the exhaust pipe when the temperature of the exhaust pipe is increased by high-temperature exhaust gasses flowing through the exhaust pipe. Therefore, it becomes easier to prevent the temperature of the exhaust pipe from rising too high.

The exhaust pipe heat-releasing system according to an embodiment of the present invention is desirably provided with a surface-coating layer that is formed on the outer peripheral face of the base included in the exhaust pipe, and that contains a crystalline inorganic material and an amorphous binder.

Since provision of the surface-coating layer that contains a crystalline inorganic material and an amorphous binder on the outer peripheral face of the base of the exhaust pipe easily leads to an increase in the emissivity of the outer peripheral face of the exhaust pipe, the amount of radiation heat from the outer peripheral face of the exhaust pipe is more likely to be increased. The radiation heat from the outer peripheral face of the exhaust pipe is more likely to be received by the heat-receiving member according to the embodiment of the present invention which demonstrates excellent performance in receiving heat.

That is, improvement in the amount of radiation heat from the outer peripheral face of the exhaust pipe is combined with improvement in the amount of heat received by the heat-receiving member. As a result, it becomes easier to more effectively prevent the temperature of the exhaust pipe from rising too high.

In the exhaust pipe heat-releasing system according to an embodiment of the present invention, the exhaust pipe desirably has an emissivity of about 0.78 or more. The emissivity falling in such a range easily leads to improvement in the amount of radiation heat from the outer peripheral face of the exhaust pipe, thereby making it easier to even more effectively prevent the temperature of the exhaust pipe from rising too high.

First Embodiment

Hereinafter, a first embodiment, which is one embodiment of a heat-receiving member and an exhaust pipe heat-releasing system according to the present invention, is described with reference to drawings.

First, the heat-receiving member according to the embodiment of the present invention is described.

FIG. 2 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 1 illustrated in FIG. 2 includes a base 20 that contains aluminum or an aluminum alloy, and a surface layer 30 formed by anodizing the surface of the base 20.

The surface layer formed by anodizing the base has emissivity higher than the emissivity of aluminum. The emissivity (infrared emissivity) at a wavelength of from about 3 μm to about 30 μm is, for example, about 0.7 or more. The infrared emissivity can be measured by a radiometer (for example, an AERD produced by Kyoto Electronics Manufacturing Co., Ltd.).

The kind of aluminum or an aluminum alloy to be used as the base is not particularly limited so long as it can be anodized. For example, pure aluminum (1000 series), Al—Cu—Mg alloys (2000 series), Al—Mn alloys (3000 series), Al—Si alloys (4000 series), Al—Mg alloys (5000 series), Al—Mg—Si alloys (6000 series), Al—Zn—Mg alloys (7000 series), or the like can be used.

The shape of the base is not particularly limited, and can be, for example, a plate such as a flat plate, a curved plate, and a flexed plate. The shape can be set to any shape according to the shape of the place in which the heat-receiving member is to be used. The base may be formed by laminating a plurality of bases.

Further, the thickness of the base is not particularly limited either, and can be set to any thickness according to the amount of heat to be received by the heat-receiving member and the expected operating temperature of the heat-receiving member.

In the case where a heat-receiving member is to be provided in the exhaust pipe heat-releasing system according to the embodiment of the present invention, the thickness of the base to be used in production of the heat-receiving member is desirably from about 0.1 mm to about 1.5 mm, more desirably from about 0.3 mm to about 1.0 mm, and even more desirably from about 0.4 mm to about 0.8 mm.

A thickness of about 0.1 mm or more of the base is less likely to make the strength insufficient. On the other hand, a thickness of about 1.5 mm or less does not easily lead to application of large compressive strain and large tensile strain to the surface layer upon deformation of the base.

In the case where the base is formed by laminating a plurality of bases, the thickness of the base is the sum of thicknesses of the laminated bases.

The thickness of the base is different before and after the anodization. Suppose that the surface of the base is taken as the reference position. When an oxide film with a thickness of ΔZ is formed on the upper side of the reference position by anodization, an oxide film with a thickness of ΔZ is to be simultaneously formed on the under side of the reference position by anodization, and thus the thickness of the base is to be decreased by ΔZ.

Accordingly, the thickness of the base used in production of the heat-receiving member can be presumed to be a thickness (ΔZ+T). The thickness (ΔZ+T) is obtained by measuring the thickness (2×ΔZ) of the surface layer and the thickness (T) of the base in the heat-receiving member after the anodization, and by adding a half of the thickness of the surface layer, which is (ΔZ), to the measured thickness (T) of the base.

The surface layer is formed by anodizing the base, that is, by passing an electric current through an electrolytic bath with the base serving as the anode.

In the case of anodizing only one surface of the base, it is desirable that a masking tape or the like be put on the surface not to be anodized, for protection.

The thickness of the surface layer is desirably from about 5 μm to about 25 μm.

A thickness of about 5 μm or more of the surface layer tends not to decrease the emissivity. On the other hand, a thickness of about 25 μm or less of the surface layer tends not to increase the rigidity of the surface layer and thus tends not to increase the thermal stress applied to the adjacent base, thereby tending not to generate a fissure in the base. Also, a thickness of about 25 μm or less of the surface layer tends not to make it difficult to perform electrolytic coloring. Further, a thickness of about 25 μm or less of the surface layer is less likely to be inefficient because it tends not to require a long time for anodization and it easily leads to achievement of much effect of improving the emissivity.

The thickness of the base and the thickness of the surface layer can be measured by observing the cross-section of the heat-receiving member with a SEM or the like.

The electrolytic bath includes an acidic bath, an alkaline bath, and a bath of a non-aqueous solution such as a formamide series and a boric acid series. The acidic bath includes a bath of an aqueous solution in which one kind or two kinds or more of the following is/are dissolved: sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfosalicylic acid, pyrophoric acid, sulfamic acid, phosphomolybdic acid, boric acid, malonic acid, succinic acid, maleic acid, citrate, tartaric acid, phthalic acid, itaconic acid, malic acid, glycolic acid, and the like.

The alkaline bath includes a bath of an aqueous solution in which one kind or two kinds or more of the following is/are dissolved: sodium hydroxide, potassium hydroxide, sodium carbonate, potassium phosphate, ammonia water, and the like.

The current waveform at the time of electrolysis includes waveforms of direct current (DC), alternate current (AC), a superposition of AC and DC, a combination of AC and DC, an imperfectly-rectified wave, a pulse wave, a rectangle wave, or the like.

The electrolytic method includes a constant current method; a constant voltage method; a constant power method; a high-speed anodizing method based on a continuous current, an intermittent current, or current recovery; and the like.

The heat-receiving member of the present embodiment may have a micropore formed in the surface layer.

FIG. 3 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 2 illustrated in FIG. 3 has a large number of micropores 40 formed in the surface layer 30.

The micropores 40 are generated in the surface layer 30 when the thickness of the surface layer 30 formed by anodization becomes about 10 nm to about 20 nm. Further, as the anodization is continued on, the thickness of the surface layer 30 tends to be increased and the depth of the micropores 40 tends to be increased, whereby the plurality of deep micropores 40 are more likely to be formed in the surface layer 30.

The heat-receiving member of the present embodiment may have a metal deposited in the micropores.

FIG. 4 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 3 illustrated in FIG. 4 has a metal 50 precipitated and deposited in the micropores 40 illustrated in FIG. 3 by electrolytic coloring.

Deposition of a metal in the micropores by electrolytic coloring is more likely to further increase the emissivity of the surface layer.

Examples of the metal to be deposited in the micropores include metals such as Ni, Cu, Co, Pd, Sn, Pb, and Cd. A particularly desirable metal among these is Ni or Co because they make it easier to increase the emissivity of the surface layer.

Further, since use of Ni makes it easy to block the pore, Ni is more desirable.

Examples of a method of depositing a metal in the micropores include a method of passing an electric current through an electrolytic bath, which includes a metal, with the surface layer formed by anodization serving as the cathode, and the like.

The kind of electrolytic bath to be used to deposit a metal is not particularly limited. For example, in the case of depositing Ni, an electrolytic bath containing nickel sulfate can be used.

Further, silicate or zirconium hydroxide may be deposited in the micropores by alternately immersing a heat-receiving member in acid or alkali and in a silicate aqueous solution or zirconium salt bath.

In the heat-receiving members as illustrated in FIGS. 3 and 4, the micropores formed in the surface layer may be blocked by a general method such as a method of immersing a heat-receiving member in boiling water, a method of immersing a heat-receiving member in hot water that contains a metal salt, or the like.

Next, the exhaust pipe heat-releasing system according to the embodiment of the present invention is described.

FIG. 5 is a cross-sectional view schematically illustrating an exemplary exhaust pipe heat-releasing system according to the embodiment of the present invention.

An exhaust pipe heat-releasing system 100 illustrated in FIG. 5 includes an exhaust pipe 101 having a cylindrical base 102 that contains a metal, and the heat-receiving member 1 according to the embodiment of the present invention arranged over the exhaust pipe 101.

The heat-receiving member 1 is arranged such that the surface layer 30 formed by anodizing the surface of the base 20 faces the outer peripheral face of the exhaust pipe 101.

In FIG. 5, the heat transferred from the outer peripheral face of the exhaust pipe 101 to the surface layer 30 of the heat-receiving member 1 is schematically shown by arrows.

The exhaust pipe 101 is a member that is connected to an internal combustion engine such as an engine and that allows high-temperature exhaust gases to flow therethrough.

Examples of the material of a base 102 that forms the exhaust pipe 101 include metals such as stainless steel, steel, iron, and copper, and nickel-based alloys such as Inconel, Hastelloy, and Invar. These metal materials have high heat conductivity, and therefore tend to contribute to improvement in heat-releasing properties of the exhaust pipe 101.

Further, these metal materials have high heat resistance, and are thus more likely to be suitably used in high-temperature conditions. By using these metal materials as the base of the exhaust pipe, the exhaust pipe is more easily allowed to have excellent resistance to thermal shock, excellent processability, excellent mechanical properties, and the like.

The shape of the base 102 is not particularly limited as long as it is a cylindrical shape. The cross-sectional shape thereof may be a substantially circular shape, or may be any other shape such as a substantially elliptical shape and a polygonal shape.

The heat-receiving member 1 tends to have the surface layer 30 with high emissivity, as described above. Hence, the heat-receiving member 1 is more likely to receive on the surface of the surface layer 30 much heat that is radiated from the outer peripheral surface of the exhaust pipe 101 upon an increase of the temperature of the exhaust pipe 101.

The shape of the heat-receiving member is not particularly limited as long as it does not disturb arrangement of the heat-receiving member over the exhaust pipe included in the exhaust pipe heat-releasing system. A shape may be acceptable for example in the case where the heat-receiving member according to the embodiment of the present invention corresponds to the heat insulator illustrated in FIG. 1 and the surface of the surface layer of the heat-receiving member faces the outer peripheral face of the exhaust pipe.

A heat-receiving member to be used in the exhaust pipe heat-releasing system according to the embodiment of the present invention is not limited to the heat-receiving member 1 illustrated in FIG. 2, and any heat-receiving member according to the embodiments of the present invention described herein may be used.

In the following, effects achieved by the heat-receiving member and the exhaust pipe heat-releasing system in the present embodiment are described.

(1) The heat-receiving member of the present embodiment has a surface layer formed by anodizing a surface of a base that contains aluminum or an aluminum alloy. The emissivity of the surface of the surface layer formed by anodization tends to be higher than the emissivity of aluminum. When the emissivity of the surface of the surface layer is high, the heat-receiving member of the present embodiment, arranged with the surface layer thereof facing the heat source such as an exhaust pipe, is more likely to receive by radiation heat transfer a large amount of heat released from the heat source. That is, the heat-receiving member of the present embodiment tends to demonstrate excellent performance in receiving, by radiation heat transfer, heat released from a heat source. Further, use of such a heat-receiving member makes it easier to promote heat release from the heat source.

(2) The heat-receiving members of the present embodiment may have micropores in the surface layer thereof, and a metal may be deposited in the micropores. When a metal is deposited in the micropores in the surface layer, the emissivity of that region tends to be more increased.

(3) The exhaust pipe heat-releasing system of the present embodiment includes an exhaust pipe having a cylindrical base that contains a metal, and a heat-receiving member according to the embodiment of the present invention arranged over the exhaust pipe.

The heat-receiving member according to the embodiment of the present invention tends to demonstrate excellent performance in receiving heat by radiation heat transfer. Such a heat-receiving member arranged over the exhaust pipe is more likely to receive much radiation heat from the outer peripheral surface of the exhaust pipe when the temperature of the exhaust pipe is increased by high-temperature gasses flowing therethrough. Thus, it becomes easier to prevent the temperature of the exhaust pipe from rising too high.

Hereinafter, Examples are described which more specifically disclose the first embodiment of the present invention. However, the present embodiment is not limited to these Examples.

EXAMPLE 1

A plate (150 mm×70 mm×0.5 mm (thickness)) made of aluminum (A1050) was prepared as the base, and the surface thereof not to be anodized was protected by sticking a masking tape. Next, the plate was anodized so that a surface layer was formed on the surface of the plate. As a result, a heat-receiving member was produced.

At the time of anodization, the electrolytic bath used was a sulfuric acid bath with a concentration of 200 g/L, and the electrolyte temperature was set to 15° C. The electrolytic method used was a multistep electrolytic method in which a low voltage (20 V) was applied in the first half of the process and a high voltage (40 V) was applied in the second half of the process. Thereafter, the plate was washed to remove the electrolytic solution.

Part of the heat-receiving member after anodization was cut and the thickness of the surface layer formed by anodization was measured at five locations by SEM. The thicknesses thereof were in the range of 15 to 20 μm.

Also, micropores were formed in the surface layer.

EXAMPLE 2

The surface layer of the heat-receiving member produced in Example 1 was then electrolytically colored, that is, nickel was deposited in the micropores in the surface layer.

The electrolytic bath used was a nickel sulfate bath. The electrolytic bath had a pH of within the range of 4 to 6, and a temperature of within the range of 5 to 30° C. The electrolytic treatment was performed by an alternate current of 5 to 60 V, with the surface layer of the heat-receiving member serving as the cathode and with a carbon rod serving as the anode. Then, blocking of the micropores was performed by immersing the heat-receiving member in deionized water and boiling the water for 15 minutes.

EXAMPLES 3 TO 5

Heat-receiving members were produced by performing anodization, electrolytic coloring, and blocking in the same way as in Example 2 except that the thicknesses of the respective bases were set to 1.0, 2.0, and 5.0 mm.

COMPARATIVE EXAMPLE 1

A base made of the same aluminum as in Example 1 without anodization and electrolytic coloring performed thereon was used as the heat-receiving member.

The heat-receiving members produced in Examples 1 to 5 and Comparative Example 1 were each evaluated for the following points.

(i) Measurement of Emissivity

The emissivity of the base before anodization, the emissivity of the surface layer of the heat-receiving member after anodization, and the emissivity of the surface layer of the heat-receiving member after electrolytic coloring were each measured by a radiometer (AERD produced by Kyoto Electronics Manufacturing Co., Ltd., wavelength: 3 to 30 μm)

(ii) Measurement of Heat-Receiving Performance

FIG. 6 is a cross-sectional view schematically illustrating a method of measuring heat-receiving performance of the heat-receiving member.

A heat-receiving performance measuring machine 200 illustrated in FIG. 6 includes a heater 201 that is surrounded by a heat insulating material 202. The heater 201 is connected to a not-shown power source through a power source cable 203, and the temperature of the heater 201 can be increased by turning the power on. The upper face of the heat-receiving performance measuring machine 200 is open so that putting the heat-receiving member 1, the effect of which is to be measured, on the open face forms a closed space around the heater 201.

The length shown by an arrow A in FIG. 6 indicates the long side (150 mm) of the heat-receiving member 1, and the length shown by an arrow B indicates the width (120 mm) of the closed space.

In measurement of the heat-receiving performance, the heat-receiving member 1 was placed on the upper face of the heat-receiving performance measuring machine 200 with the surface layer 30 facing the heater 201 side, and then the heater 201 was powered on.

Next, the amount of electricity was adjusted so that the amounts of the radiation heat and the input electricity would be equal when the temperature of the heater was 500° C., and the amount of electricity at this time was recorded.

The recorded amount of electricity was set to be the amount of heat received by the heat-receiving member.

It should be noted that the heat-receiving member of Comparative Example 1, which has no surface layer formed therein, was placed with the surface of the base facing the heater side.

Further, the temperature of the heat-receiving member was measured at five locations when the amounts of the radiation heat and the input electricity were equalized with the temperature of the heater being 500° C.

The measuring locations were the points shown by arrows C, D, E, F, and G, which were set by dividing at 30 mm intervals the width of 120 mm shown by the arrow B in FIG. 6.

Here, the measuring locations are aligned at the midpoint (35 mm) of the short side (70 mm) of the heat-receiving member, and therefore the location E in FIG. 6 corresponds to the center of the heat-receiving member.

Thereafter, the largest value and the smallest value among the temperatures measured at the five locations were derived, and then a value resulting from “the largest value−the smallest value” was used as an index that shows the variation of the temperature distribution inside the heat-receiving member.

(iii) Measurement of Thermal Distortion

Displacement of the location E in FIG. 6 in the measurement test of the heat-receiving performance in (ii) was measured by a non-contact type displacement meter.

(iv) Measurement of Fissures in Base

The heat-receiving members produced in Examples 1 to 5 and Comparative Example 1 were tested by 500 cycles of a temperature cycle test in which a cycle of heating up to 250° C. and cooling down to 25° C. by water immersion was repeated. Then, the base after the temperature cycle test was visually observed to see whether a fissure was generated therein.

The evaluation results of the points (i) to (iv) with respect to the heat-receiving members produced in Examples 1 to 5 and Comparative Example 1 are shown together in Table 1.

Table 1 shows the temperatures of the location E in FIG. 6. In Examples 1 to 5 and Comparative Example 1, the temperature was highest at the location E, namely at the center of the heat-receiving member.

With respect to generation of fissures, a heat-receiving member with a very small fissure generated therein is shown as “+”, and a heat-receiving member with a large fissure generated therein is shown as “−”.

TABLE 1 Heat-receiving member Evaluation result Thick- Temper- Amount of ness ature at Highest Lowest Tempereature heat Amount of of base Electrolytic Emis- location E temperature temperature difference reception distortion (mm) Anodization coloring sivity (° C.) (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 1 0.5 performed not 0.780 448 448 418 30 2798 2.5 + performed Example 2 0.5 performed performed 0.814 452 452 423 29 2817 2.6 + Example 3 1.0 performed performed 0.814 452 452 421 31 2810 0.6 + Example 4 2.0 performed performed 0.814 438 438 419 19 2747 0.3 + Example 5 5.0 performed performed 0.814 418 418 407 11 2617 0.3 + Comparative 0.5 not not 0.050 315 315 299 16 1755 1.9 − Example 1 performed performed

Here, the emissivity of the surface layer formed by anodization in Example 1 was considerably higher than the emissivity of the unanodized base in Comparative Example 1. Further, the amount of heat received by the heat-receiving member in Example 1 was larger than the amount of heat received by the heat-receiving member in Comparative Example 1.

Since the amount of electricity, which was measured as the amount of heat received, is equal to the amount of radiation heat from the heater as the heat source, the heat release from the heat source is considered to be easily accelerated by use of a heat-receiving member with high emissivity as in Example 1.

Further, it is assumed that electrolytic coloring as in Example 2 makes it easier to further increase the emissivity of the heat-receiving member, and in this case, the amount of heat received is presumably further increased.

Example 2 and Examples 3 to 5 were compared to find out the effect of thickness of the base. In every Example, the emissivity of the surface of the heat-receiving member with a surface layer formed thereon was 0.814.

The highest temperature was observed at the location E in every Example, and when the thickness of the base was increased to 2.0 mm or to 5.0 mm, the highest temperature was decreased according to the increase thereof. Further, when the thickness of the base was increased to 2.0 mm or to 5.0 mm, the temperature difference between the highest temperature and the lowest temperature was decreased according to the increase of the thickness of the base.

The reason for a decrease in the temperature difference according to the increase of the thickness of the base has not been revealed. However, the reason is considered to be that the amount of heat transferred within the base by heat conduction tends to be increased when the thickness of the base is large, and that the temperatures within the heat-receiving member thus tend to be equalized.

Furthermore, the amount of distortion in the heat-receiving member was decreased according to the increase of the thickness of the base. This is presumably because a large thickness of the base more easily enhances the strength of the base and thereby tends not to generate a deformation of the base due to the thermal stress.

With respect to generation of fissures in the base, a very small fissure was observed in the base of the heat-receiving members in Examples 1 to 5.

On the other hand, a large fissure was generated in the base in Comparative Example 1. The large fissure in the base was presumably caused by the heat resistance of an unanodized aluminum base which is lower than the heat resistance of an anodized aluminum base.

Second Embodiment

Next, a second embodiment, which is one embodiment of the heat-receiving member of the present invention, is described with reference to the drawings.

In the heat-receiving member of the second embodiment, the emissivity of one region far from the high-temperature part of the heat source is higher than the emissivity of another region.

FIG. 7 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 4 illustrated in FIG. 7 has the surface layer 30 that is formed by anodizing the surface of the base 20, and the surface layer 30 has a large number of the micropores 40 formed therein.

Part of one region in the surface layer 30 is electrolytically colored, and thus the micropores 40 in the region have the metal 50 deposited therein. Another region in the surface layer 30 is not electrolytically colored, and thus the micropores 40 in these regions do not have the metal 50 deposited therein.

In the heat-receiving member 4, the region on which electrolytic coloring was performed (high-emissivity region) has emissivity higher than the emissivity of the region on which electrolytic coloring was not performed, and the region on which electrolytic coloring was not performed (low-emissivity region) has emissivity lower than the emissivity of the region on which electrolytic coloring was performed.

Examples of the method of producing the heat-receiving member 4 include a method in which, after the surface layer has been formed by anodization in the same way as in the method of producing the heat-receiving member in the first embodiment, the region not to be electrolytically colored is masked at the time of the electrolytic coloring.

The masking can be carried out by a method such as sticking a masking tape on the region.

As a result, the masking more easily allows the unmasked region to be a high-emissivity region, and more easily allows the masked region to be a low-emissivity region.

FIG. 8 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 5 illustrated in FIG. 8 has the surface layer 30 formed by anodizing a part of the base 20. Another part of the base 20 is unanodized, and thus the surface of the base 20 is exposed.

In the heat-receiving member 5, the region with the surface layer 30 formed therein by anodization (high-emissivity region) has emissivity higher than that of the region with the surface of the base 20 exposed thereon. On the other hand, the region with the surface of the base 20 exposed thereon (low-emissivity region) has emissivity lower than that of the region with the surface layer 30 formed therein. The region with the surface of the base exposed thereon is arranged at a location close to the high-temperature part of the heat source.

Examples of the method of producing the heat-receiving member 5 include a method in which a region not to be anodized is masked and then anodized upon production of a heat-receiving member in the first embodiment.

The masking can be carried out by a method such as sticking a masking tape on the region.

As a result, the masking more easily allows the unmasked region to be a high-emissivity region, and more easily allows the masked region be a low-emissivity region.

FIG. 9 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 6 illustrated in FIG. 9 has the surface layer 30 formed by anodizing a part of the base 20. Further, the surface layer 30 is electrolytically colored, and thus the micropores 40 have the metal 50 deposited therein. Another part of the base 20 is not anodized and thus the surface of the base 20 is exposed.

In the heat-receiving member 6, the anodized and electrolytically colored region (high-emissivity region) has emissivity higher than that of the region with the surface of the base 20 exposed thereon. On the other hand, the region with the surface of the base 20 exposed thereon (low-emissivity region) has emissivity lower than that of the anodized and electrolytically colored region.

In the heat-receiving member 6, the difference in the emissivity between the high-emissivity region and the low-emissivity region is larger than the difference in the emissivity between the high-emissivity region and the low-emissivity region in the heat-receiving member 4 and the heat-receiving member 5.

Examples of the method of producing the heat-receiving member 6 include a method in which a region not to be anodized is masked before anodization, and with the region being masked, the micropores are formed and the surface layer is then electrolytically colored.

More specifically, further anodizing the produced heat-receiving member 5 so as to form micropores in the surface layer and then further electrolytically coloring the surface layer results in production of the heat-receiving member 6.

In the heat-receiving member of the second embodiment, the size of the region with emissivity lower than that of the another region is desirably from about 5% to about 95% of the total surface area.

Further, the size of the area with emissivity lower than that of the another region is desirably larger than a size of about 10 mm×about 10 mm when the shape of the region is substantially rectangular.

Also, the difference in the emissivity between the high-emissivity region and the low-emissivity region is desirably from about 0.01 to about 0.90.

Furthermore, a ratio (Y/X) of a length (Y) of the short side of the region with emissivity lower than that of the another region to a thickness (X) of the base is desirably about 2 or more.

In the following, effects of the heat-receiving member of the present embodiment are described.

In the present embodiment, in addition to the effects (1) and (2) described in the first embodiment, the following effects can be achieved.

(4) In the heat-receiving member of the present embodiment, there is a region with emissivity higher than that of another region. Since the region having higher emissivity than emissivity of the another region is more likely to receive heat by radiation heat transfer, the amount of heat to be received per unit area tends to be large. The region having higher emissivity than that of the another region is thus more likely to be a region in which the temperature tends to rise due to reception of heat. Accordingly, placing the region having higher emissivity than the another region at a location far from the high-temperature part of the adjacent heat source makes it more likely for the temperature of the heat-receiving member to rise even if a region is located far from the high-temperature part of the heat source; hence, generation of a low-temperature region inside the heat-receiving member is more likely to be prevented.

That is, generation of a temperature difference inside the heat-receiving member is more likely to be prevented. Further, generation of thermal stress and distortion in the heat-receiving member is more likely to be prevented.

(5) In the heat-receiving member of the present embodiment, micropores may be formed in the surface layer in the region far from the high-temperature part of the heat source, and a metal may be deposited in the micropores.

Deposition of a metal in the micropores in the surface layer makes it easier to increase the emissivity of the region. That is, placing the region with a metal deposited in the micropores formed in the surface layer thereof at a location far from the high-temperature part of the heat source makes it easier to more effectively prevent generation of a low-temperature region inside the heat-receiving member.

(6) In the heat-receiving member of the present embodiment, a region close to the high-temperature part of the heat source may include a region in which the surface of the base is unanodized and exposed.

Since the base is made of aluminum or an aluminum alloy, the emissivity of the region with the surface of the base exposed thereon tends to be low. Placing the region with the surface of the base exposed thereon at a location close to the high-temperature part of the heat source makes it easier to prevent the temperature of the heat-receiving member from rising too high even if a region is located close to the high-temperature part of the heat source; hence, generation of a high-temperature region inside the heat-receiving member is more likely to be prevented. That is, generation of a temperature difference inside the heat-receiving member is more likely to be prevented.

Hereinafter, Examples are described which more specifically disclose the second embodiment of the present invention. However, the present embodiment is not limited to these Examples.

EXAMPLE 6

A base made of aluminum was anodized to form a surface layer on the base and to form micropores in the surface layer, in the same way as in Example 1.

Next, at the center (the location E in FIG. 6) of the anodized surface, a masking tape (851T, produced by Sumitomo 3M Limited.) with a size of 20 mm×20 mm was stuck.

Subsequently, the surface layer was electrolytically colored in the same way as in Example 2, and thereby nickel was deposited in the micropores in the region without the masking tape stuck thereon.

Thereafter, the masking tape was removed, and then blocking was carried out in the same way as in Example 2.

A heat-receiving member produced thereby has a region on which electrolytic coloring was not performed, which is a “low-emissivity region”, and a region on which electrolytic coloring was performed, which is a “high-emissivity region”.

EXAMPLE 7

At the center (the location E in FIG. 6) of the to-be anodized surface of the base that is of the same kind as the base used in Example 1, a masking tape with a size of 10 mm×10 mm was stuck.

Then, the base was anodized in the same way as in Example 1, and a surface layer was formed by anodization on a region without a masking tape stuck thereon, and further, micropores were formed in the surface layer.

Subsequently, the surface layer was electrolytically colored in the same way as in Example 2, and thereby nickel was deposited in the micropores in the region without the masking tape stuck thereon.

Thereafter, the masking tape was removed, and then blocking was carried out in the same way as in Example 2.

A heat-receiving member produced thereby has a region on which anodization and electrolytic coloring were not performed, which is a “low-emissivity region”, and a region on which anodization and electrolytic coloring were performed, which is a “high-emissivity region”.

EXAMPLES 8 AND 9

Heat-receiving members were produced by the same method as in Example 7 except that the respective masking tapes had a size of 20 mm×20 mm and a size of 50 mm×50 mm.

EXAMPLES 10 TO 12

Heat-receiving members were produced by the same method as in Example 7 except that the bases each had a thickness of 1.0 mm and the respective masking tapes had a size of 10 mm×10 mm, a size of 20 mm×20 mm, and a size of 50 mm×50 mm.

EXAMPLES 13 TO 15

Heat-receiving members were produced by the same method as in Example 7 except that the bases each had a thickness of 2.0 mm and the respective masking tapes had a size of 10 mm×10 mm, a size of 20 mm×20 mm, and a size of 50 mm×50 mm.

EXAMPLES 16 TO 18

Heat-receiving members were produced by the same method as in Example 7 except that the bases each had a thickness of 5.0 mm and the respective masking tapes had a size of 10 mm×10 mm, a size of 20 mm×20 mm, and a size of 50 mm×50 mm.

The heat-receiving members produced in Examples 6 to 18 were evaluated for the same points (i) to (iv) as in Example 1.

First, evaluation results of the heat-receiving members of Examples 6 to 9 each with the base having a thickness of 0.5 mm are shown together in Table 2. For comparison, the result of the heat-receiving member of Example 2 which had uniform emissivity on the surface thereof is also shown.

TABLE 2 Heat-receiving member Evaluation result Thickness Low-emissivity region Highest Lowest of base Electrolytic Size temperature temperature (mm) Anodization coloring Emissivity (mm × mm) (° C.) (° C.) Example 2 0.5 N/A N/A N/A N/A 452 423 Example 6 0.5 performed not 0.780 20 × 20 424 418 performed Example 7 0.5 not not 0.050 10 × 10 439 409 performed performed Example 8 0.5 not not 0.050 20 × 20 402 379 performed performed Example 9 0.5 not not 0.050 50 × 50 392 359 performed performed Evaluation result Temperature Amount of Temperature Temperature decrease at heat Amount of difference at location E location E reception distortion (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 2 29 452 0 2817 2.6 + Example 6 6 424 28 2674 2.3 + Example 7 30 439 13 2709 1.2 + Example 8 23 379 73 2452 2.0 + Example 9 33 359 93 2302 1.3 +

Table 2 shows the emissivities of the low-emissivity regions in Examples 2 and Examples 6 to 9. In Example 6 in which the heat-receiving members were anodized and the low-emissivity region thereof was not electrolytically colored, the emissivity was 0.780. In Examples 7 to 9 in which the low-emissivity regions in the heat-receiving members were not anodized nor electrolytically colored, the emissivity was 0.050, the same as that of the base.

Although Table 2 does not show the emissivities of the high-emissivity regions and the emissivity in Example 2, those emissivities correspond to the emissivities of the anodized and electrolytically colored regions, and thus those emissivities are all 0.814.

The heat-receiving member of Example 2 with uniform emissivity on the surface thereof had the highest temperature of 452° C. at the location E in the heat-receiving member shown in FIG. 6, that is, at the center of the heat-receiving member.

On the other hand, the heat-receiving members of Examples 6 to 9, each of which had a low-emissivity region at the location E, had a temperature lower than the temperature of the heat-receiving member of Example 2 at the location E. Table 2 shows as “temperature decrease at location E” how many degrees the temperature dropped from the temperature at the location E in Example 2.

Further, Table 3 shows the temperatures measured at the locations C, D, E, F, and G shown in FIG. 6, for Example 2 and Examples 6 to 9. Furthermore, FIG. 10 shows the relationships between the locations of temperature measurement and the temperatures of the respective heat-receiving members, which were measured in Example 2 and Examples 6 to 9.

TABLE 3 Heat-receiving member Thickness Low-emissivity region Evaluation result of base Electrolytic Size Location C Location D Location E Location F Location G (mm) Anodization coloring Emissivity (mm × mm) (° C.) (° C.) (° C.) (° C.) (° C.) Example 2 0.5 N/A N/A N/A N/A 423 439 452 447 423 Example 6 0.5 performed not 0.780 20 × 20 418 419 424 418 418 performed Example 7 0.5 not not 0.050 10 × 10 410 426 439 434 409 performed performed Example 8 0.5 not not 0.050 20 × 20 400 392 379 389 402 performed performed Example 9 0.5 not not 0.050 50 × 50 390 367 359 363 392 performed performed

Hereinafter, the evaluation results are described with reference to Table 2, Table 3, and FIG. 10.

In Example 6, the emissivity of the low-emissivity region is 0.780, and the difference between this emissivity and the emissivity of 0.814 of the high-emissivity region is 0.034. Such provision of a high-emissivity region and a low-emissivity region in the heat-receiving member decreases the temperature at the location E by 28° C.; thus, the temperature difference between the highest temperature and the lowest temperature became 6° C., which presumably made it easier to bring the temperature distribution within the heat-receiving member closer to the uniform distribution.

In Example 8, the emissivity of the low-emissivity region was 0.05, which led to a large decrease in the temperature at the location E by 73° C. From comparison with Example 6 in which the area of the low-emissivity region is 20 mm×20 mm, the same area as in Example 8, it is assumed that lower emissivity in the low-emissivity region tends to more greatly increase temperature-decrease effects.

From comparison among Examples 7 to 9 each having the same emissivity of 0.05 in the low-emissivity region and having a different area of the low-emissivity region, it is assumed that a larger area of the low-emissivity region more easily leads to a larger temperature decrease at the location E.

Also, in each of Examples 8 and 9 in which the temperature decrease was large, the temperature was lowest at the location E within the heat-receiving member, and thus the line of the line chart of Examples 8 and 9 in FIG. 10 had a reverse shape of the line for Example 2.

From those results, it is assumed that provision of a high-emissivity region and a low-emissivity region in the heat-receiving member makes it easier to prevent the temperature from rising too high in a certain region within the heat-receiving member, and to prevent the temperature from falling too low in a certain region. It is also assumed that appropriately adjusting the emissivities and sizes in the high-emissivity region and in the low-emissivity region makes it easier to adjust the temperature distribution inside the heat-receiving member.

Next, the evaluation results of Examples 10 to 12 in which the bases each had a thickness of 1.0 mm, Examples 13 to 15 in which the bases each had a thickness of 2.0 mm, and Examples 16 to 18 in which the bases each had a thickness of 5.0 mm are respectively shown in Table 4, 5, or 6.

For comparison, the result of the heat-receiving member of Example 3, 4, or 5 with uniform emissivity on the surface thereof is also shown. The respective values of “temperature decrease at location E” were calculated based on the temperature at the location E in Example 3, 4, or 5.

TABLE 4 Heat-receiving member Evaluation result Thickness Low-emissivity region Highest Lowest of base Electrolytic Size temperature temperature (mm) Anodization coloring Emissivity (mm × mm) (° C.) (° C.) Example 3 1.0 N/A N/A N/A N/A 452 421 Example 1.0 not not 0.050 10 × 10 443 410 10 performed performed Example 1.0 not not 0.050 20 × 20 405 387 11 performed performed Example 1.0 not not 0.050 50 × 50 394 362 12 performed performed Evaluation result Temperature Amount of Temperature Temperature decrease at heat Amount of difference at location E location E reception distortion (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 3 31 452 0 2810 0.6 + Example 33 443 9 2738 0.5 + 10 Example 18 387 65 2486 0.5 + 11 Example 32 362 90 2332 0.8 + 12

TABLE 5 Heat-receiving member Evaluation result Thickness Low-emissivity region Highest Lowest of base Electrolytic Size temperature temperature (mm) Anodization coloring Emissivity (mm × mm) (° C.) (° C.) Example 4 2.0 N/A N/A N/A N/A 438 419 Example 2.0 not not 0.050 10 × 10 426 412 13 performed performed Example 2.0 not not 0.050 20 × 20 404 393 14 performed performed Example 2.0 not not 0.050 50 × 50 394 373 15 performed performed Evaluation result Temperature Amount of Temperature Temperature decrease at heat Amount of difference at location E location E reception distortion (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 4 19 438 0 2747 0.3 + Example 14 426 12 2669 0.4 + 13 Example 11 393 45 2495 0.4 + 14 Example 21 373 65 2363 0.4 + 15

TABLE 6 Heat-receiving member Evaluation result Thickness Low-emissivity region Highest Lowest of base Electrolytic Size temperature temperature (mm) Anodization coloring Emissivity (mm × mm) (° C.) (° C.) Example 5 5.0 N/A N/A N/A N/A 418 407 Example 5.0 not not 0.050 10 × 10 412 407 16 performed performed Example 5.0 not not 0.050 20 × 20 402 391 17 performed performed Example 5.0 not not 0.050 50 × 50 395 387 18 performed performed Evaluation result Temperature Amount of Temperature Temperature decrease at heat Amount of difference at location E location E reception distortion (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 5 11 418 0 2617 0.3 + Example 7 412 6 2585 0.3 + 16 Example 11 391 27 2480 0.3 + 17 Example 8 387 31 2440 0.4 + 18

From the results shown in Table 2 and Tables 4 to 6, effects exerted on the characteristics of the heat-receiving member by the thickness of the base were studied.

When the heat-receiving members of Examples with the respective bases having the same thickness are compared, the larger the size of the low-emissivity region, the larger the temperature decrease at the location E.

Comparison of the results of the heat-receiving members of Examples with the same sizes of the low emissivity regions and with different thicknesses of the bases showed that the larger the thickness of the base, the smaller the temperature decrease tended to be.

Although the reason for this has not been revealed, it is assumed that, since a larger thickness of the base more easily leads to a larger amount of heat transferred inside the base by heat conduction, influences of an increase/decrease of the emissivity thereby tend to be small.

Also, the larger the thickness of the base, the smaller the amount of distortion tended to be. The reason for this is considered to be that the mechanical strength of the base tends to be increased as the thickness of the base is increased.

From these results, it is assumed that appropriately adjusting the emissivities and sizes of the high-emissivity region and the low-emissivity region according to the thickness of the base makes it easier to adjust the temperature distribution inside the heat-receiving member.

Third Embodiment

Now, a third embodiment, which is one embodiment of the heat-receiving member of the present invention, is described with reference to the drawings.

The heat-receiving member in the third embodiment has a plurality of cracks formed in the surface layer thereof.

FIG. 11 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 7 illustrated in FIG. 11 has the surface layer 30 formed by anodizing the surface of the base 20, and the surface layer 30 has a plurality of cracks 60 formed therein.

FIG. 12, FIG. 13, and FIG. 14 each are a scanning electron microscope photograph that shows a surface of a surface layer of an exemplary heat-receiving member according to the embodiment of the present invention which has cracks in the surface layer.

In the surface layer shown in FIG. 12, a crack 61 has a zigzag shape as shown in the encircled region.

In the surface layer shown in FIG. 13, a crack 62 is in a state where at least one end thereof has stopped growing and thus is not connected to another crack, as shown in the encircled region; the cracks are separated from each other.

In the surface layer shown in FIG. 14, cracks 63 are formed as straight lines substantially parallel to each other in one direction, as shown by arrows.

The width of each crack is desirably from about 0.01 μm to about 15 μm.

A width of about 15 μm or less makes it difficult to generate a fissure in the base.

Examples of the method of forming cracks in the surface layer include a method in which the heat-receiving member after anodization is bent so that it is distorted, and then the heat-receiving member is bent again so that it restores the original shape.

In the following, effects of the heat-receiving member of the present embodiment are described.

In the present embodiment, the following effects can be exerted in addition to the effects (1) and (2) that have been described in the first embodiment.

(7) The plurality of cracks are formed in the surface layer of the heat-receiving member of the present embodiment. Therefore, part of thermal stress, which is applied between the base and the surface layer, is more likely to be absorbed at the cracked part. As a result, the thermal stress applied between the base and the surface layer is more likely to be prevented from becoming large. As a result, generation of a fissure in the base due to the thermal stress is more likely to be prevented.

(8) In the heat-receiving member of the present embodiment, the cracks may be separated from each other.

In the case where the cracks are separated from each other, the cracks tend to absorb the thermal stress and to grow upon application of the thermal stress to the surface layer, and thus make it easier to effectively prevent generation of a fissure in the base. Further, the continuous surface layer is more likely to increase the rigidity and thus makes it easier for the heat-receiving member to maintain the shape.

(9) In the heat-receiving member of the present embodiment, at least one of the cracks may have a zigzag shape.

A zigzag shape of the crack tends to generate resistance to the force applied in the direction parallel to the crack, and therefore makes it easier to effectively prevent generation of a fissure in the base.

Hereinafter, Examples are described which more specifically disclose the third embodiment of the present invention. However, the present embodiment is not limited to these Examples.

EXAMPLE 19

A heat-receiving member was produced in the same way as in Example 2. Thereafter, the produced heat-receiving member was bended by hand to add distortion to the heat-receiving member. Then, cracks attributed from the distortion were observed.

The cracks had a zigzag shape, and had widths of 0.01 to 15 μm at five locations when measured by SEM.

The heat-receiving member produced in Example 19 was evaluated for the same points (i) to (iv) as in Example 1. The results thereof are shown together in Table 7. For comparison, the result of the heat-receiving member of Example 2 with no crack formed in the surface layer thereof is also shown.

TABLE 7 Heat-receiving member Evaluation result Thickness Temper- Highest Lowest Amount of of ature at temper- temper- Temperature heat Amount of base Electrolytic Emis- location E ature ature difference reception distortion (mm) Anodization coloring Crack sivity (° C.) (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 2 0.5 performed performed not 0.814 452 452 423 29 2817 2.6 + formed Example 19 0.5 performed performed formed 0.806 449 449 421 28 2784 1.9 ++

The heat-receiving member produced in Example 19 had emissivity slightly lower than that of the heat-receiving member of Example 2. This decrease is considered to be due to inclusion of the surface of the base, which appeared at the cracked part, in the region the emissivity of which was measured.

In the heat-receiving member produced in Example 19, no fissure was observed in the base because of the cracks.

This result is shown as “++” in Table 7.

Fourth Embodiment

Now, a fourth embodiment, which is one embodiment of the heat-receiving member of the present invention, is described with reference to the drawings.

The heat-receiving member of the fourth embodiment has surface layers formed by anodizing both respective surfaces of the base thereof.

FIG. 15 is a cross-sectional view schematically illustrating an exemplary heat-receiving member according to the embodiment of the present invention.

A heat-receiving member 11 illustrated in FIG. 15 has the base 20 both surfaces of which are anodized, and the base 20 has a surface layer 30 a on the upper surface, and has a surface layer 30 b on the lower surface.

The surface layer 30 a and the surface layer 30 b respectively have micropores 40 a and micropores 40 b formed therein, and the micropores 40 a and the micropores 40 b respectively have a metal 50 a and a metal 50 b deposited therein.

That is, the structure of one side of the heat-receiving member is the same as that of the heat-receiving member illustrated in FIG. 4.

The heat-receiving member illustrated in FIG. 15 is an exemplary heat-receiving member of the present embodiment. As the surface layer of the heat-receiving member of the present embodiment, any of the surface layers of the heat-receiving members that have been described thus far can be employed.

Further, the conditions of the surface layer on the upper surface and lower surface may be different. Examples of such a structure include a structure in which the surface layer on the upper surface is electrolytically colored and the surface layer on the lower surface is not electrolytically colored, and the like.

Examples of a method of forming surface layers by anodizing both respective surfaces of the base include a method in which the base without masking performed thereon is immersed into an electrolytic bath such that both surfaces of the base touch the electrolytic bath, and the like. Alternatively, one surface of the base may be anodized at one time.

In the following, effects of the heat-receiving member of the present embodiment are described.

In the present embodiment, changing the structure of the surface layer makes it possible to achieve the following effects on the respective surfaces in addition to achievement of the respective effects (1) and (2) and effects (4) to (9), the effects having been described in the first to third embodiments.

(10) In the heat-receiving member of the present embodiment, surface layers are formed by anodizing both respective surfaces of the heat-receiving member, and thus the emissivity of the both surfaces of the heat-receiving member tends to be high. As a result, it becomes easier for the heat-receiving member to receive much heat on one surface and release much heat from the other surface. Therefore, the temperature of the heat-receiving member tends not to rise, which makes it easier to decrease the thermal stress generated in the heat-receiving member.

Further, the lower the temperature of the heat-receiving member, the larger the amount of heat that the heat-receiving member can receive tends to be; hence, the temperature of the heat-receiving member tends not to rise even at the time of heat reception, which makes it easier to produce a heat-receiving member that demonstrates excellent performance in receiving heat by radiation heat transfer.

In the following, Examples are described which more specifically disclose the fourth embodiment of the present invention. However, the present embodiment is not limited to these Examples.

EXAMPLE 20

A same base as the base used in Example 1 was immersed in an electrolytic bath without a masking tape being stuck on the base, and then both surfaces of the base were anodized to form respective surface layers on the both surfaces of the base. Then, micropores were further formed in the surface layers.

Other conditions of anodization were same as those in Example 1.

Next, a masking tape was stuck for protection on the surface layer formed on a surface of the base which was to be a heat-releasing face when the base is used as a heat-receiving member. Then, the surface layer was electrolytically colored in the same way as in Example 2 so that nickel was deposited in the micropores.

Thereafter, the masking tape was removed and blocking was carried out in the same way as in Example 2.

In a heat-receiving member produced as thus described, one of the surfaces was anodized and electrolytically colored and the other surface was only anodized.

EXAMPLE 21

A heat-receiving member was produced in the same way as in Example 20 except that a masking tape was not stuck on the surface layer before electrolytic coloring in Example 20.

In a heat-receiving member produced as thus described, both faces were anodized and electrolytically colored.

The heat-receiving members produced in Examples 20 and 21 were evaluated for the same points (i) to (iv) as in Example 1. In Example 20, the heat-receiving member was placed such that the anodized and electrolytically colored surface faced the heaters and thus was used as a heat-receiving face. Further, the surface, which was only anodized, was arranged on the other side and set to be the heat-releasing face. In Example 21, the sides that the surfaces of the heat-receiving member would face were optionally determined.

Furthermore, Example 22 and Example 23 as described below were carried out.

EXAMPLE 22

In Example 22, a same heat-receiving member as that produced in Example 20 was used in measurement of heat-receiving performance. However, unlike in Example 20, the heat-receiving member was placed in reverse, that is, the surface on which only anodization was performed was used as the heat-receiving face, and the surface on which anodization and electrolytic coloring were performed was used as the heat-releasing face.

EXAMPLE 23

In Example 23, a same heat-receiving member as that produced in Example 2 was used in measurement of heat-receiving performance. However, unlike in Example 2, the heat-receiving member was placed in reverse, that is, the surface layer of the heat-receiving member was arranged on the farther side from the heaters and thus was used as the heat-releasing face, and the surface on which anodization was not performed was used as the heat-receiving face.

The results of evaluation of Examples 20 to 23 are shown together in Table 8. For comparison, the result of the heat-receiving member of Example 2 is also shown.

TABLE 8 Heat-receiving member Thickness Heat-receiving face Heat-releasing face of base Electrolytic Electrolytic (mm) Anodization coloring Emissivity Anodization coloring Emissivity Example 2 0.5 performed performed 0.814 not not 0.050 performed performed Example 20 0.5 performed performed 0.814 performed not 0.780 performed Example 21 0.5 performed performed 0.814 performed performed 0.814 Example 22 0.5 performed not 0.780 performed performed 0.814 performed Example 23 0.5 not not 0.050 performed performed 0.814 performed performed Evaluation result Amount of Temperature Highest Lowest Temperature heat Amount of at location E temperature temperature difference reception distortion (° C.) (° C.) (° C.) (° C.) (W/m²) (mm) Fissure Example 2 452 452 453 29 2817 2.6 + Example 20 372 372 357 15 8848 1.7 + Example 21 366 366 346 20 9059 1.5 + Example 22 356 356 340 16 8768 1.6 + Example 23 136 136 127 9 1788 1.3 +

In each of Examples 20 to 22, since the emissivity is high both on the heat-receiving face and the heat-releasing face of the heat-receiving member, the amount of heat reception is more than 8700 W/m². This amount of heat reception is very large compared to the result of the heat-receiving member of Example 2 which has high emissivity only on the heat-receiving face.

That is, it is assumed that, in Examples 20 to 22, a large amount of heat release from the heat-receiving face by radiation heat transfer tends to considerably increase the amount of heat reception of the heat-receiving member.

Further, the highest temperature of the heat-receiving member is low despite the large amount of heat reception, which leads to an assumption that heat release from the heat-receiving member is more likely to be promoted.

It should be noted that the amount of heat reception was small in Example 23 in which the heat-receiving member had high emissivity only on the heat-releasing face and had low emissivity on the heat-receiving face.

From these results, it is assumed that providing respective surface layers on both surfaces of the heat-receiving member by anodization so as to increase the emissivity on a heat-receiving face and a heat-releasing face makes it easier to produce a heat-receiving member which demonstrates excellent performance in receiving heat by radiation heat transfer.

Fifth Embodiment

Next, a fifth embodiment, which is one embodiment of the exhaust pipe heat-releasing system of the present invention, is described with reference to the drawings.

In the exhaust pipe heat-releasing system of the present embodiment, a surface-coating layer containing a crystalline inorganic material and an amorphous binder is formed on the outer peripheral face of the exhaust pipe described in the exhaust pipe heat-releasing system of the first embodiment.

FIG. 16 is a cross-sectional view schematically illustrating an exemplary exhaust pipe heat-releasing system according to the embodiment of the present invention.

An exhaust pipe 151 that forms an exhaust pipe heat-releasing system 150 illustrated in FIG. 16 has a cylindrical base 102 that contains a metal; and a surface-coating layer 103 containing a crystalline inorganic material and an amorphous binder, which is formed on the outer peripheral face of the base 102.

Further, the heat-receiving member 1 is placed such that the surface layer 30 formed by anodization faces the surface-coating layer 103 of the exhaust pipe 151.

Arrows illustrated in FIG. 16 schematically show heat transferred from the surface-coating layer 103, which is formed on the outer peripheral face of the exhaust pipe 151, to the surface layer 30 of the heat-receiving member 1.

The surface-coating layer 103 has an emissivity of about 0.78 or more at a wavelength of from about 3 μm to about 30 μm. Provision of the surface-coating layer 103 with high emissivity on the outer peripheral face of the exhaust pipe 151 makes it easier to effectively release heat in the exhaust pipe 151 to the outside of the exhaust pipe 151 by radiation heat transfer.

The material of the crystalline inorganic material contained in the surface-coating layer 103 is not particularly limited. An oxide of a transition metal is desirably used, and specific examples thereof include manganese dioxide, manganese oxide, iron oxide, cobalt oxide, copper oxide, chrome oxide and nickel oxide. Each of these may be used alone or two or more kinds of these may be used in combination.

These oxides of transition metals are suitably used for producing crystalline inorganic materials having high emissivity.

Examples of the amorphous binder include barium glass, boron glass, strontium glass, alumina-silicate glass, soda-zinc glass and soda-barium glass. Each of these may be used alone or two or more kinds of these may be used in combination.

Such an amorphous binder is a low-melting-point glass and its softening temperature is in the range of about 400° C. to about 1100° C. Accordingly, melting the amorphous inorganic binder to coat the outer peripheral face of the base of the exhaust pipe and then firing the base make it easier to form a robust surface-coating layer on the outer peripheral face of the base.

When the amorphous binder is a low-melting-point glass, the melting point thereof is desirably in the range of about 400° C. to about 1100° C.

When the low-melting-point glass has a melting point of about 400° C. or more, the glass is less likely to easily soften during use and extraneous matters tend not to adhere to the glass. On the other hand, when the melting point is about 1100° C. or less, the heating in formation of a surface-coating layer is less likely to deteriorate the base.

In the surface-coating layer containing the crystalline inorganic material and the amorphous binder, with respect to a compounding amount of the crystalline inorganic material, a desirable lower limit is about 10% by weight and a desirable upper limit is about 90% by weight.

When the compounding amount of the crystalline inorganic material is about 10% by weight or more, the infrared emissivity is less likely to be insufficient and the heat-releasing property in a high-temperature region is less likely to be inferior. On the other hand, when the compounding amount is about 90% by weight or less, the adhesion between the heat-releasing layer and the base of the exhaust pipe is less likely to be lowered.

With respect to the compounding amount of the crystalline inorganic material, a more desirable lower limit is about 30% by weight and a more desirable upper limit is about 70% by weight.

It is desirable that the surface-coating layer have a thickness of from about 0.5 μm to about 10 μm.

When the surface-coating layer has a thickness of about 0.5 μm or more, a sufficient heat-releasing property is more likely to be ensured. On the other hand, when the surface-coating layer has a thickness of about 10 μm or less, cracks tend not to appear on the surface-coating layer and the exhaust pipe tends not to be deformed.

It is desirable that the surface-coating layer is formed on the entire outer peripheral face of the exhaust pipe because, in this case, the area of the surface-coating layer will easily be largest and the surface-coating layer will easily have a particularly excellent heat-releasing property. However, a surface-coating layer may be formed only on a part of the outer peripheral face of the exhaust pipe; particularly when the surface-coating layer is formed on the surface that faces the heat-receiving member, it may not be formed on other parts on the exhaust pipe.

Hereinafter, a method of producing an exhaust pipe to be used in the exhaust pipe heat-releasing system of the present embodiment is described in accordance with the order of processes.

(I) Using a cylindrical exhaust pipe processed into a predetermined shape as a starting material, cleaning is performed so as to remove impurities on a surface of the base of the exhaust pipe.

The cleaning is not particularly limited, and conventionally known cleaning may be used. More specifically, ultrasonic cleaning in alcohol solvent, and the like may be used.

Further, after the cleaning, roughening may be optionally performed on the surface of the base of the exhaust pipe in order to enlarge a specific surface area of the outer peripheral face of the base of the exhaust pipe or to adjust the maximum height Rz of the inner face of the base of the exhaust pipe. More specifically, roughening such as sandblasting, etching and high-temperature oxidation may be performed. Each of the treatments may be used alone or two or more kinds of these may be used in combination.

(II) Separately, a crystalline inorganic material and an amorphous binder are wet-mixed so as to prepare a raw material composition for a surface-coating layer.

More specifically, a powder of a crystalline inorganic material and a powder of an amorphous binder are prepared so that each has a predetermined particle size, a predetermined shape, and the like. Respective powders are dry-mixed at a predetermined compounding ratio to obtain a mixed powder. Then, water is added thereto and the mixture is wet-mixed by ball milling so as to prepare a raw material composition for a surface-coating layer.

The compounding ratio of the mixed powder and water is not particularly limited. However, about 100 parts by weight of water with respect to 100 parts by weight of a mixed powder is desirable. The reason for this is that a viscosity suitable for applying to the base of the exhaust pipe can be obtained. According to need, an inorganic fiber or an organic solvent may be blended to the raw material composition for a surface-coating layer.

(III) The outer peripheral face of the base of the exhaust pipe is coated with the raw material composition for a surface-coating layer.

As a method for coating with the raw material composition for a surface-coating layer, for example, spray coating; electrostatic coating; ink jet; transfer using a stamp, a roller or the like; brush coating and the like may be used.

In addition, the base of the exhaust pipe may be immersed in the raw material composition for a surface-coating layer so as to be coated with the raw material composition for a surface-coating layer.

At least one of plating such as nickel plating and chrome plating, oxidation of the outer peripheral face of the metal base, and the like may be performed before the coating of the outer peripheral face of a base of the exhaust pipe with a raw material composition for a surface-coating layer.

The reason for this is that there is a case where an adhesion property between a base of the exhaust pipe and a surface-coating layer is improved.

(IV) The exhaust pipe coated with the raw material composition for a surface-coating layer is fired.

More specifically, after the exhaust pipe coated with the raw material composition for a surface-coating layer is dried, a surface-coating layer is formed by firing.

The firing temperature is desirably set to the melting point of the amorphous binder or higher, and it is desirably from about 700° C. to about 1100° C. The firing temperature depends on the kind of the blended amorphous binder. By setting the firing temperature to the melting point of the amorphous binder or higher, the exhaust pipe and the amorphous binder are more easily adhered solidly, so that a surface-coating layer solidly adhered to the base is more easily formed.

Through such processes, an exhaust pipe to be used in the exhaust pipe heat-releasing system of the present embodiment can be produced.

In the following, effects of the exhaust pipe heat-releasing system of the present embodiment are described.

The exhaust pipe heat-releasing system of the present embodiment can achieve the following effects in addition to the effect (3) described in the first embodiment.

(11) The exhaust pipe heat-releasing system of the present embodiment is provided with a surface-coating layer that contains a crystalline inorganic material and an amorphous binder on the outer peripheral face of the base of the exhaust pipe.

Provision of a surface-coating layer containing a crystalline inorganic material and an amorphous binder tends to increase the emissivity of the outer peripheral face of the exhaust pipe, thereby tending to increase the amount of radiation heat from the outer peripheral face of the exhaust pipe. Then, the radiation heat from the outer peripheral face of the exhaust pipe is more likely to be received by the heat-receiving member according to the embodiment of the present invention which demonstrates excellent performance in receiving heat.

That is, improvement in the amount of radiation heat from the outer peripheral face of the exhaust pipe is combined with improvement in the amount of heat received by the heat-receiving member, which makes it easier to more effectively prevent the temperature of the exhaust pipe from rising too high.

(12) The exhaust pipe of the exhaust pipe heat-releasing system of the present embodiment has an emissivity (emissivity of the surface-coating layer) of about 0.78 or more. Emissivity of the exhaust pipe in such a range tends to increase the amount of radiation heat from the outer peripheral face of the exhaust pipe. As a result, it becomes easier to still more effectively prevent the temperature of the exhaust pipe from rising too high.

Other Embodiments

In the case where a heat-receiving member according to any one of the embodiments of the present invention is used as a heat-receiving member for receiving heat from an exhaust manifold of an engine, the heat-receiving member may be arranged as a different member from a heat insulator.

FIG. 17 is an exploded perspective view schematically illustrating exemplary arrangement of the heat-receiving member according to the embodiment of the present invention as a different member from the heat insulator.

In FIG. 17, the heat-receiving member 1 according to the embodiment of the present invention is arranged between the exhaust manifold 111 and the heat insulator 118, with the surface layer 30 of the heat-receiving member 1 being on the exhaust manifold 111 side.

Even such arrangement of a heat-receiving member makes it easier to increase the cooling ability of an exhaust manifold.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein. 

1. A heat-receiving member comprising: a base having a surface and comprising at least one of aluminum and an aluminum alloy; and a surface layer provided at the surface of the base, the surface layer being anodized.
 2. The heat-receiving member according to claim 1, wherein the heat-receiving member has a first region and a second region, the first region and the second region being to be located so that a distance between the first region and a high-temperature part of a heat source is larger than a distance between the second region and the high-temperature part, and wherein the first region has emissivity higher than emissivity of the second region.
 3. The heat-receiving member according to claim 2, wherein said surface layer is provided in the first region and has a micropore in which a metal is deposited.
 4. The heat-receiving member according to claim 2, wherein said second region has an unanodized and exposed surface of the base.
 5. The heat-receiving member according to claim 1, wherein the surface layer has a plurality of cracks.
 6. The heat-receiving member according to claim 1, wherein the surface of the base comprises a first surface and a second surface located opposite to the first surface, the surface layer being provided at each of the first surface and the second surface.
 7. An exhaust pipe heat-releasing system comprising: an exhaust pipe comprising a metal; and a heat-receiving member arranged to face a periphery of said exhaust pipe to receive heat energy released from the exhaust pipe, the heat-receiving member comprising: a base having a surface and comprising at least one of aluminum and an aluminum alloy; and a surface layer provided at the surface of the base, the surface layer being anodized.
 8. The exhaust pipe heat-releasing system according to claim 7, wherein the heat-receiving member has a first region and a second region, the first region and the second region being to be located so that a distance between the first region and a high-temperature part of the exhaust pipe is larger than a distance between the second region and the high-temperature part, and wherein the first region has emissivity higher than emissivity of the second region.
 9. The exhaust pipe heat-releasing system according to claim 8, wherein the surface layer is provided in said first region and has a micropore in which a metal is deposited.
 10. The heat-receiving member according to claim 1, wherein the heat-receiving member is configured to receive heat energy released from a heat source. 